expression
when one was a very young child; very early in one's life
Refers to the period of early childhood; often used in reminiscences or to describe formative experiences.
幼い頃、よく祖母に絵本を読んでもらった。
When I was a very young child, my grandmother often read picture books to me.
幼い頃の思い出は、今でも鮮明に覚えている。
I still vividly remember my memories from very early in my life.
Refers to one's childhood in general, not specifically very early childhood.
Phrase composed of 幼い (osana-i, 'very young') + 頃 (koro, 'time, period').